At Ostia, at the Tiber’s mouth, historical tradition said that there had been Romans settled since the days of King Ancus Marcius, and that, even earlier, Aeneas had landed there and built a camp. In 1938 the great Italian archaeologist Guido Calza began soundings to ascertain the date of the oldest surviving stratum. The area he chose was beneath Ostia’s Imperial Forum, where the two main streets, the _cardo_ and the _decumanus_, crossed. (The Via Ostiensis, from Rome to the river mouth, determined the line of the _decumanus_.) What he found (Fig. 4.2) was a set of walls enclosing a rectangle 627 feet long and 406 feet wide. The wall was built of roughly squared blocks of tufa in a technique not unlike that of Rome’s wall of 378 B.C., but since there was Fidenae stone in it, Calza dated the wall somewhat later than 378. The wall was pierced by four gates of two rooms each, with portcullis. The south gate was demolished in the early Empire to provide space for a temple of Rome and Augustus; the north gate gave way under Hadrian to the massive podium of a Capitolium, but the footings of the east and west gates survive, well below the level of the Imperial pavement. Calza found drains within the walls, and traces of four other streets (unpaved) besides the _cardo_ and _decumanus_, but no identifiable buildings. Some terracotta revetments found in the area suggest an unidentified temple of the third century B.C. No traces earlier than the late fourth-century wall have been found in the excavated area of Ostia. Either Ancus Marcius’ foundation is a myth, or it was planted in some thus far undiscovered spot, of which all the plowing and digging in the neighborhood has left no trace. [Illustration: FIG. 4.2 Ostia, _castrum_, plan. (G. Calza, _Scavi di Ostia_, 1, fac. p. 68)]